The present invention relates to novel halo-derivative addition compounds useful as flame retardant agents for polymeric compositions, to a process for their preparation and to flame retarded polymer compositions containing said novel compounds. More particularly, the invention relates to novel, halo-derivative addition compounds useful as flame retardant agents and to polymeric compositions containing them.
Halogen-containing compounds are commonly used for the fire retardation of numerous polymeric materials. Such fire retardants, depending on their chemistry, can be applied in two forms, according to whether they are reacted into the polymeric structure or not. In the first case they become permanently incorporated into the polymer structure: fire retardants that behave in this manner will be called "active fire retardants". In the second case they form a mixture with the preformed polymeric material and will be called "additive fire retardants" or briefly "additives".
The use of an additive fire retardant does not involve any chemical interaction between the polymeric substrate and the additive, which is merely dissolved or dispersed in the polymer matrix and therefore can be lost from the substrate in various ways. Typical example of the latter are materials with appreciable vapor pressure which may vaporize out, incompatible materials which bleed and soluble materials which can be leached out. Therefore, it is clear that where the chemical and physical properties of the polymer permit, an active fire retardant is generally preferable.
It is commonly recognized in the field of fire retardant technology that the efficacy of an active fire retardant is greater than that of an additive fire retardant. On the other hand, mere additives are more easily incorporated into the plastic mass and are generally more versatile, both with respect to substrate choice and concentration levels employable. The latter point is particularly important, since fire retardants are often more expensive than the polymer itself and not every application requires the same degree of fire retardation. Thus the amount of additive to be added is optimally variable.
Although the flame retardant polymer compositions obtained by the incorporation of these novel flame retardant agents according to the present invention are by themselves very efficient, one may further enhance their effectiveness by including one or more synergists conventionally used in flame retardation. These synergistic compounds include organo-phosphorus compounds, oxides, sulfides or organic salts of antimony, boron, arsenic or zinc borate. The preferred synergistic compounds for use in the compositions of this invention are organo-phosphorus compounds and antimony oxide.
For some purposes, it might be desirable to incorporate in the polymeric composition an additional flame retardant in order to obtain a particular property. Such additional flame retardants may be e.g. halogenated compounds, such as decabromodiphenyl ether, brominated polystyrene, poly-(pentabromobenzyl acrylate) and dodecachloro-dodecahydrodimethanodibenzo-cyclooctene, hydrated oxides, such as hydrated alumina and hydrated magnesia, or other commonly employed compounds, such as melamine cyanurate. Also other common plastics ingredients such as fillers, pigments, lubricants, smoke suppressants, plasticisers, antioxidants etc., may be incorporated.
As known in the art, another problem with fire retarded polymeric materials is their enhanced sensitivity to ultraviolet light irradiation, leading to discoloration thereof. Furthermore, a common deficiency in the use of simple additive flame retardants is their tendency to migrate to the surface during fabrication of the finished product, giving rise to a disfiguration called "bloom".
Polymeric flame retardants have been developed in an attempt to take advantage of the positive characteristics of simple additives, yet minimize their deficiencies. Such materials are usually expensive to manufacture and often do not have suitable physico-chemical properties.